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Smartphone-based behavioral interventions for weight loss were more effective when they involved financial incentives or one-on-one coaching calls, two randomized trials showed.

In , middle-age men with obesity who received a financial incentive along with behavior-focused text messages lost 3.2 percentage points more of their body weight at 12 months compared with men not receiving texts or a financial incentive (P<0.001), reported Pat Hoddinott, MBBS, PhD, of Stirling University in Scotland, and colleagues in JAMA.

Men who only received texts lost a non-significant 1.4 percentage points more body weight than the men with no intervention (P=0.05).

In the , middle-age participants using a smartphone app-based feedback system for weight management lost an average 2 kg more at 6 months if they also received weekly phone coaching calls (P<0.001), reported Bonnie Spring, PhD, of Northwestern University Feinberg School of Medicine in Chicago, and colleagues in JAMA.

Ideal weight loss goals for people with obesity is at least 5% of body weight, "with at least 10% weight loss conferring greater cardiometabolic health benefits," noted Jamy D. Ard, MD, of Wake Forest University School of Medicine in Winston-Salem, North Carolina, and colleagues in an .

The treatment effects in these studies were modest compared to what's possible with GLP-1 receptor agonists, "and the likelihood that these lifestyle interventions could lead to long-term weight loss maintenance is low," the editorialists wrote. Yet the studies still "present interesting innovations that have implications for the practice of obesity medicine," including the fact that the first trial successfully engaged men with obesity.

"Given that many patients with obesity do not want or cannot access medical or surgical treatments, innovative and effective behavioral interventions that are low-intensity and relatively easy to disseminate, such as those described in these studies, may still be important in the evolving landscape of obesity treatment," they added.

Monetary Motivation

The first study involved 585 men with a body mass index (BMI) of at least 30 (mean BMI 37.7), all living in Belfast, Ireland, Bristol, England, or Glasgow, Scotland, and enrolled from July 2021 to May 2022. The men were predominantly white (90%), with an average age of 50.7, and 39% lived in lower socioeconomic areas.

All participants received weight management information and a pedometer. For 12 months, 194 men received text messages focused on behaviors that help lose weight, and 196 men received the same text messages along with a financial incentive paid if they met weight loss targets. The remaining 195 men were put on a waiting list as a control group.

The texts "incorporated weight management evidence, website links to information resources, and theory-based behavior change techniques based on the Health Action Process Approach, self-determination theory, and the behavior change maintenance model," Hoddinott and team explained. The most texts the men could receive during the trial was 370, including three weight appointment reminders and three notifications of weight goal attainment, but they could pause, resume, or adjust the frequency of them.

The financial incentive was $64 for losing 5% of body weight at 3 months, $191 for losing 10% at 6 months, and $254 for maintaining the 10% loss at 12 months, totaling up to $490 if they met all goals.

The primary endpoint was the difference in weight loss between the control group and each of the intervention groups, with 3% set as the minimum clinically important difference.

The men receiving texts and financial incentives lost a mean 5.7 kg, equivalent to -4.8% of their body weight, at 12 months, compared with 1.5 kg (-1.3%) in the control group. The text-only group lost a mean 3 kg, or -2.7% of their body weight. A mean 332 texts were sent during the trial, and a mean $159 per participant was paid in the financial incentive group; 62% of that group received payments, including 15% who received the full amount.

To lose at least 5% of body weight, the number needed to treat in the financial incentive and text group was 4, compared with 15 in the text-only group.

The most common adverse events were infections (23%), and none of the 23 serious adverse events across the groups was determined to be linked to the trial.

"Although the technology and financial incentive approach used in this trial could be scaled to reach broad audiences, questions remain about the durability of the effect, particularly in a competitive and crowded phone app market," the editorialists wrote. Furthermore, "there is concern for maladaptive behaviors, such as overly restrictive eating or excessive exercise, motivated by the financial incentive."

Coaching Call Success

The second study was a noninferiority trial based in the U.S. Among 400 participants with a mean BMI of 34.4 who were enrolled from June 2017 to March 2021, 199 used a wireless feedback system (WFS) for 3 months, while the other 201 used the WFS and received once-weekly telephone coaching for 3 months. Mean age was 40.5, 76.3% were women, about 20% were Black, and 66.5% were white.

The WFS was a Wifi activity tracker (Fitbit Zip) and scale that transmitted data to a smartphone app with daily feedback on progress. Goals included calorie and saturated fat intake limits and an initial 60 minutes of weekly physical activity that gradually rose to 300 minutes in increments based on each participant's previous week's activity.

The once-weekly calls, lasting 10-15 minutes from health coaches with access to the participants' progress data, involved motivational interviewing, goal-setting, problem-solving, and tech support. The coaches were supervised by licensed clinical health psychologists.

If participants were not making progress in meeting the goal of 5% body weight loss at 6 months, step-up interventions included phone notifications from the app, phone coaching if they were not already receiving it, and powdered meal replacement for those already receiving calls.

At 6 months, 85.5% of participants had outcome data available, showing a mean 2.8-kg loss in the WFS group (95% CI -3.5 to -2.0) and a mean 4.8-kg loss in the group with WFS and coaching (95% CI -5.5 to -4.1). Half the participants received step-up interventions, split between the groups in similar proportions.

At 12 months, the coached group had lost a mean 1.7 kg more from baseline than the WFS-only group (95% CI -2.9 to -0.5). Among non-responders, however, no significant differences in weight loss occurred between the groups at 3, 6, or 12 months.